The field of the invention is tools and techniques for servicing pipelines. More specifically, the invention relates to tools and techniques for temporarily stopping flow in a pipeline.
Various tools and techniques have successfully been used in the past to stop flow of liquids or gases in pipelines. These tools are typically used to temporarily stop flow, to allow a downstream section of pipeline to be inspected, repaired, changed, or otherwise serviced. Such stopping or sealing tools are often used in emergency situations to stop flow within a localized section of pipeline, when flow cannot be quickly or easily stopped using existing valves in the pipeline. These tools are also used for planned operations or maintenance. In pipelines made of materials such as polyethylene, or similar plastics which can be deformed without damage, squeeze or pinch tools have been used to temporarily stop flow. These types of tools squeeze or pinch the pipeline flat to stop flow. When removed, the pipeline returns to its original or near original typically round shape, allowing flow to resume. For rigid or non-deformable pipelines, made of e.g., steel or iron, various stopping or plugging tools have been used. Some of these stopping or plugging tools can also be used with plastic pipe if the pinch method is not desired. With these tools, typically an opening is cut or drilled into the pipeline through a pressure housing. The stopping tool then installs a plug or similar stopping element into the pipeline to stop flow. The stopping element is removed when service is complete, allowing flow to resume. Leakage of gas or liquid from the pipeline during the stopping operation is minimized or eliminated via the pressure housing.
As described in International Patent Application PCT/US/01/31468, incorporated herein by reference, fiber optic conduit or cable may be advantageously installed within existing pipelines, to provide high speed communication links, without the need for routing cable or conduit along new right of ways or without the drawbacks of new underground conduit installation.
Placing fiber optic cable or conduit within existing natural gas pipelines has recently become much more viable, with the development of systems and methods for installing the cables while the pipeline remains in service. Especially in urban areas where trenching to lay cable is difficult, time consuming, and costly, and where virtually all buildings are already connected to a natural gas pipeline network, the use of fiber optic cable within natural gas pipelines has many advantages.
However, existing tools and techniques used for stopping flow in a natural gas pipeline are not usable for pipelines containing a cable. With the cable or conduit laying on the bottom of the pipeline, the stopping or sealing elements currently in use cannot achieve an effective seal within the pipeline (since the flow area inside the pipeline is no longer a circular cross section). In addition, regardless of the lack of effective sealing characteristics, use of existing stopping or sealing tools and techniques in pipelines containing a cable involves significant risk of crushing, severing or otherwise damaging the cable.
Accordingly, with the introduction of cable into pipelines, there is a need for flow stopping tools and techniques, which are compatible with a cable or conduit in the pipeline.
The invention provides tools and techniques for stopping flow in a pipeline containing a cable. The tools may be used on pipelines above ground, or with minimum trenching and exposure of buried pipelines. The tools provide an effective seal within the pipeline, stopping flow, without damaging the cable in the pipeline. The tools may be used at any location along pipeline. Generally, each tool seals against the inside round walls of the pipeline, and also around the outside of the cable.
In a first aspect, a tool for pinching off flow of gas through a deformable or plastic pipeline includes an actuator on an armature. The actuator moves an upper plate towards a lower plate. Displacement members on the lower plate help to guide the cable within the pipeline into a recess in the lower plate. This allows the pipeline to be squeezed flat to stop flow, without crushing the cable. The displacement members are preferably rollers or lever arms. The displacement members are advantageously urged into an up or extended position by springs.
In a second aspect, a tool for sealing off gas flow, in a rigid (e.g., steel) pipeline, or in a deformable or plastic pipeline containing a cable, has a seal ring on a handle. A linkage on the handle drives seal lips on the seal ring to engage around and seal against the cable within the pipeline. The outside circular edges of the seal ring seal against the inside walls of the pipeline. Preferably, the drive linkage includes jaws engaged with the seal lips. A rod advantageously extends through the handle and is connected to the jaws, for remote operation of the jaws.
In a third aspect of the invention, a stopper tool for use in a pipeline containing a cable or conduit has first and second plates pivotably attached to a center plate. A resilient seal ring overlies the first, second and center plate. A linkage pivots the first and second plates from an open position, where the first and second plates are oriented at an angle to the center plate, to a second position where, the first and second plates generally lie within the same plane as the center plate. The tool is installed into the pipeline with the plates in the first position. Once appropriately located within the pipeline, the first and second plates are pivoted into the second position, creating a seal within the pipeline.
In a fourth aspect of the invention, a pipeline flow stopper tool has a resilient plug including first and second lips positioned to fit over a cable within a pipeline. As the plug is pushed into the pipeline, the plug deforms and seals against the pipeline walls. The first and second lips extend around and under the cable, forming a continuous seal around the cable within the pipeline.
Other and further objects and features will become apparent from the following detailed description. The invention resides as well in subcombinations of the assemblies, components and steps described. Each of the tools described is intended for use in a pipeline having a specific inside diameter of e.g., 5-100 cm. Consequently, typically tools including any of the aspects described above will be available in a range of sizes. The tools are also intended for use with a cable or conduit of a known and specified diameter within the pipeline.
It is an object of the invention to provide tools and techniques for stopping flow within a pipeline containing a cable or conduit.